var textarea = document.querySelector('textarea');
textarea.addEventListener('click', function () {
    if (textarea.value !== '备注') {
        textarea.style.color = "#000";
    }
})

var buttons = document.querySelectorAll('button');
for (var i = 0; i < 3; i++) {
    buttons[i].onclick = function () {
        for (var i = 0; i < 3; i++) {
            buttons[i].style.backgroundColor = "#F4F4F4";
            buttons[i].style.color = "#717171";
            buttons[i].style.border = "1px solid #ccc";
        }
        this.style.backgroundColor = "skyblue";
        this.style.border = "1px solid skyblue";
        this.style.color = "#fff";
    }
}